RE: [squid-users] squid 3.2.0.5 smp scaling issues

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> Date: Sun, 12 Jun 2011 22:47:25 +1200
> From: squid3_at_treenet.co.nz
> To: squid-users_at_squid-cache.org
> Subject: Re: [squid-users] squid 3.2.0.5 smp scaling issues
>
> On 12/06/11 22:20, Jenny Lee wrote:
> >
> >> Date: Sun, 12 Jun 2011 03:02:23 -0700
> >> From: david_at_lang.hm
> >> To: bodycare_5_at_live.com
> >> CC: squid3_at_treenet.co.nz; squid-users_at_squid-cache.org
> >> Subject: RE: [squid-users] squid 3.2.0.5 smp scaling issues
> >>
> >> On Sun, 12 Jun 2011, Jenny Lee wrote:
> >>
> >>>> On 12/06/11 18:46, Jenny Lee wrote:
> >>>>>
> >>>>> On Sat, Jun 11, 2011 at 9:40 PM, Jenny Lee wrote:
> >>>>>
> >>>>> I like to know how you are able to do>13000 requests/sec.
> >>>>> tcp_fin_timeout is 60 seconds default on all *NIXes and available ephemeral port range is 64K.
> >>>>> I can't do more than 1K requests/sec even with tcp_tw_reuse/tcp_tw_recycle with ab. I get commBind errors due to connections in TIME_WAIT.
> >>>>> Any tuning options suggested for RHEL6 x64?
> >>>>> Jenny
> >>>>>
> >>>>> I would have a concern using both those at the same time. reuse and recycle. Reuse a socket, but recycle it, I've seen issues when testing my own linux distro's with both of these settings. Right or wrong that was my experience.
> >>>>> fin_timeout, if you have a good connection, there should be no reason that a system takes 60 seconds to send out a fin. Cut that in half, if not by 2/3's
> >>>>> And what is your limitation at 1K requests/sec, load (if so look at I/O) Network saturation? Maybe I missed an earlier thread and I too would tilt my head at 13K requests sec!
> >>>>> Tory
> >>>>> ---
> >>>>>
> >>>>>
> >>>>> As I mentioned, my limitation is the ephemeral ports tied up with TIME_WAIT. TIME_WAIT issue is a known factor when you are doing testing.
> >>>>>
> >>>>> When you are tuning, you apply options one at a time. tw_reuse/tc_recycle were not used togeter and I had 10 sec fin_timeout which made no difference.
> >>>>>
> >>>>> Jenny
> >>>>>
> >>>>>
> >>>>> nb: i still dont know how to do indenting/quoting with this hotmail... after 10 years.
> >>>>>
> >>>>
> >>>> Couple of thing to note.
> >>>> Firstly that this was an ab (apache bench) reported figure. It
> >>>> calculates the software limitation based on speed of transactions done.
> >>>> Not necessarily accounting for things like TIME_WAIT. Particularly if it
> >>>> was extrapolated from say, 50K requests, which would not hit that OS limit.
> >>>
> >>> Ab accounts for 200-OK responses and TIME_WAITS cause squid to issue 500. Of course if you send in 50K it would not be subject to this but I usually send couple 10+ million to simulate load at least for a while.
> >>>
> >>>
> >>>> He also mentioned using a "local IP address". If that was on the lo
> >>>> interface. It would not be subject to things like TIME_WAIT or RTT lag.
> >>>
> >>> When I was running my benches on loopback, I had tons of TIME_WAITS for 127.0.0.1 and squid would bail out with: "commBind: Cannot bind socket..."
> >>>
> >>> Of course, I might be doing things wrong.
> >>>
> >>> I am interested in what to optimize on RHEL6 OS level to achieve higher requests per second.
> >>>
> >>> Jenny
> >>
> >> I'll post my configs when I get back to the office, but one thing is that
> >> if you send requests faster than they can be serviced the pending requests
> >> build up until you start getting timeouts. so I have to tinker with the
> >> number of requests that can be sent in parallel to keep the request rate
> >> below this point.
> >>
> >> note that when I removed the long list of ACLs I was able to get this 13K
> >> requests/sec rate going from machine A to squid on machine B to apache on
> >> machine C so it's not a localhost thing.
> >>
> >> getting up to the 13K rate on apache does require doing some tuning and
> >> tweaking of apache, stock configs that include dozens of dynamically
> >> loaded modules just can't achieve these speeds. These are also fairly
> >> beefy boxes, dual quad core opterons with 64G ram and 1G ethernet
> >> (multiple cards, but I haven't tried trunking them yet)
> >>
> >> David Lang
> >
> >
> > Ok, I am assuming that persistent-connections are on. This doesn't simulate any real life scenario.
>
> What do you mean by that? it is the basic requirement for access to the
> major HTTP/1.1 performance features. ON is the default.
 
 
 
First of all, this breaks tcp_outgoing_address in squid. So it is definitely off for me.
 
Above issue also makes persistent-connections unusable for peers.
 
Second, when you have many users going to many destinations, persistent-connections is of no use. Even though I have persistent connections on for the client site, I am still bitten by the ephemeral ports.
 
These are my scenarios.
 
 

> > I would like to know if anyone can do more than 500 reqs/sec with persistent connections off.
> >
> > Jenny
>
> Good question. Anyone?
 
I can do 450 reqs/sec under constant load. But no more. And I have tried all available TCP tuning options.
 
Jenny
Received on Sun Jun 12 2011 - 11:22:24 MDT